body, div, ul, li, img {
	margin:0;
	padding:0;
	list-style:none;
}
.box {
	position:relative;
	width:500px;
	height:330px;
	margin:50px auto;
	overflow:hidden; /*只显示当前图片，隐藏其余图片。没有此属性，图片会列成一排*/
}
.box ul:first-of-type {
	position:absolute;
	top:0;
	left:0;
	width:3000px;
}
.box ul:first-of-type li {
	float:left;
}
.box ul:last-of-type {
	position:absolute;
	right:10px;
	bottom:10px;
}
.box ul:last-of-type li {
	float:left;
	width:20px;
	height:20px;
	line-height:20px;
	text-align:center;
	vertical-align:middle;
	border-radius:50%;
	margin-left:10px;
	background-color:#999;
	cursor:pointer;
}
.box ul:last-of-type li.active {
	background-color:#55d5d5;
}
.buttons span {
	position:absolute;
	width:40px;
	height:40px;
	line-height:38px;
	top:50%;
	margin-top:-20px;
	text-align:center;
	font-weight:bold;
	font-size:30px;
	border:1px solid #fff;
	opacity:0.3;
	color:#fff;
	cursor:pointer;
	background-color:black;
}
.buttons span:first-of-type {
	left:0px;
}
.buttons span:last-of-type {
	left:100%;
	margin-left:-40px;
}
@media screen and (max-width:680px){
	.box {
		width:300px;
		height:198px;
	}
	.box ul:first-of-type li img {
		width:300px;
		height:198px;
	}
	.box ul:first-of-type {
		width:1800px;
	}
	.buttons span {
		width:20px;
		height:20px;
		line-height:18px;
		margin-top:-10px;
		font-size:20px;
	}
	.buttons span:last-of-type {
		margin-left:-20px;
	}
}